12 INTRODUCTORY 



treatment of organic synthesis is a complete departure from the usual 

 practice of classifying carbon compounds under types representing 

 certain atomic configurations of molecules. According to this method, 

 with which most students of organic chemistry are familiar, the 

 parent-compound or type is naturally looked upon as the generator of 

 all its derivatives, and is accordingly given the first rank in the order 

 of treatment. According to the present scheme each vital product is 

 in itself a biochemical type quite independently of the chemical type 

 to which it may be referred, and the synthesis of each product, instead 

 of being mentioned incidentally in connexion with the group to which 

 it belongs as a point of minor interest, is here brought into the first 

 rank of importance. In other words, the chemical type is in this work 

 subordinated to the individual compound a mode of treatment for 

 which every justification will be conceded when it is pointed out 

 that in vital syntheses there are unquestionable genetic relationships 

 between compounds of quite different types. 



In fact, a general survey of the present state of synthetical chemistry 

 makes it perfectly clear that the transformations in the living organism 

 have little or no relations to the chemical type, and it is equally certain 

 that the parent-compound or type, which is often the actual generator 

 in the laboratory synthesis, is not the generator in the vital synthesis. 

 Genetic relationships between vital products are thus to the student of 

 biochemistry all-important, because they may be indicative of the actual 

 course of the vital chemical transition from one compound to another, 

 while relationships due to the possession of a common type of molecular 

 structure are of subsidiary importance. Whole groups of phenols, 

 aldehydes, acids, &c., are, for example, derivatives of benzene, and this 

 hydrocarbon is their actual laboratory generator. It may be confidently 

 asserted that the synthesis of these phenols, aldehydes, acids, &c., is not 

 effected by the animal or plant via benzene any more than that the 

 formation of alizarin in the madder plant proceeds from anthracene, 

 or that the production of hydrojuglone in the walnut-tree is preceded 

 by the synthesis of naphthalene. 



On the other hand, the genetic relationships between compounds 

 of such different types as acetoacetic ester and quinol [71], as di- 

 acetyl [113] and quinol, or as y-acetobutyric ester (from acetoacetic 

 ester and glycerol) and resorcinol [70] are of special interest from our 

 present standpoint, and may prove hereafter to be of real biochemical 

 significance. The subordination of the type to the individual vital 

 product has for the foregoing reasons been consistently carried out, so 

 that benzene, for example, is treated of, as it were incidentally, in 

 connexion with the first compound in the work in which the benzene 

 nucleus occurs, viz. cymene [6], anthracene in connexion with meta- 

 hydroxyanthraquinone [144], &c. 



Another result which may be said to be accidental to the present 

 mode of treatment is the disproportionate amount of space allotted to 



